1. Field of the Invention
The present invention relates to a zoom finder of a real image type used in a 35 mm lens shutter camera, a video camera, an electronic still camera, etc.
2. Description of the Related Art
A finder for a 35 mm lens shutter camera having a zoom lens is generally constructed by a reversed Galilean finder for observing a virtual image formed by an objective lens through an eyepiece. However, the finder of this type has the problems that lens diameter is ultimately increased when zoom ratio is increased.
In contrast to this, a Keplerian finder for forming a real image by an objective lens and observing this image through an eyepiece has the advantages that lens diameter can be reduced even when zoom ratio is increased although the entire length of the finder is increased.
Recently, the thickness of the camera has been thick by the increase in zoom ratio of a photographing lens and the Keplerian finder has been utilized in the zoom finder having a large zoom ratio.
For example, in Japanese Patent Application Laying Open (KOKAI) No. 62-7017, a zooming operation is performed by the Keplerian finder. In this case, when the zoom ratio of this finder is about 3 times, the difference in diopter between wide angle and telescopic ends and an intermediate position becomes large so that it is not practical as the finder when the zoom ratio is increased.
Further, the Keplerian finder for correcting the above difference in diopter caused by the zooming operation is shown in Japanese Patent Application Laying Open (KOKAI) Nos. 61-156018 and 61-16073. In such finders, with respect to first and second groups of lenses, the zooming operation is performed by displacing the second lens group and the change in diopter caused by this zooming operation is corrected by displacing the first lens group. In this case, the moving amount of the first lens group for correcting the difference in diopter is large so that it is difficult to design a mechanism for moving the lenses, which is not necessarily practical.